This invention relates in general to dynamo-electric machines, and more particularly to improvements in gap winding type dynamo-electric machines having armature windings disposed along the inner periphery of a stator core which does not have winding slots.
In the usual dynamo-electric machine, the coils constituting the stator windings are accommodated in slots in the stator core inner periphery. However, to cope with the recent trend to provide dynamo-electric machines having increasing capacity, it is expedient to utilize the so-called gap winding type dynamo-electric machine, which is advantageous in view of its performance and the reduction of size, weight and cost of manufacture associated with such a machine construction.
The gap winding type dynamo-electric machine comprises a stator, a rotor spaced therefrom and electrically insulated armature windings disposed in the air gap between stator and rotor. The armature windings are usually secured to the stator side by suitable fixed support means. With this construction, the outer diameter of the stator core is reduced compared to the conventional dynamo-electric machine having winding slots to an extent coresponding to the depth dimension of the slot, thus permitting reduction of the overall outer diameter dimension of the stator and hence reduction of the weight of the overall machine. An example of such a machine is disclosed in U.S. Pat. No. 3,529,192 granted to Evan John Davies Sept. 15, 1970.
While it is thus advantageous to adopt the gap winding type system, problems can arise in connection with the support of the armature windings on the stator core since the armature windings are disposed along the inner periphery of the slotless stator core as mentioned earlier.
For supporting the armature windings along the inner periphery of the stator core, it has been standard practice to secure the armature windings to a winding support frame which is in turn mounted on the inner side of the stator core, or to secure the armature windings near the opposite ends thereof by support means provided at opposite ends of the stator core. When the armature windings are supported in accordance with these methods, and particularly where the armature windings are secured not to a central portion of the stator core but to the opposite ends thereof, upon sudden change of load or sudden inflow of short-circuit current, the armature winding experiences in the portion thereof corresponding to the central portion of the stator core forces acting in the circumferential direction. These forces give rise to restraining forces since the armature winding is secured at its opposite ends to the opposite ends of the stator core. Thus, often times deformation of the armature winding or damage to the insulation thereof occurs, leading to a serious accident in the extreme case. These support methods are therefore lacking in reliability.